Field of Invention
The invention relates to an anodization sealing process for an aluminum or aluminum alloy element for vehicles.
Related Art
At present, high gloss, semigloss or satin-like gloss decorative or structural elements made from aluminum plates or aluminum profiles, are used inside or outside of many vehicles, which not only have a high ornamental effect but also have a protective effect. The highly ornamental surface of the elements is achieved through different pretreatment processes including mechanical polishing, abrasive blasting, drawing, electrolytic polishing and etching, before oxidization. In order to provide the highly ornamental surface with a good protective property, the anodized film has to be sealed after the anode is oxidized.
The conventional sealing process for an aluminum or aluminum alloy element for vehicles includes two steps. In other words, the anodized film will have a good erosion resistance through the cooperation of cold sealing with warm sealing. However, the aluminum or aluminum alloy elements made from this process could only be erosion resistant within the range of pH 1.5-11.5 or 1.5-12.5.
In Europe and the United States, the automatic vehicle cleaning device is more and more widely used. In such a device, alkali cleaning agent of pH 13.5 is used. As such, in the process of impregnation before cleaning, if the vehicle equipped with aluminum or aluminum alloy anodization members is subject to the cleaning agent, the vehicle will soon turn into a milky color and lose the aesthetic appearance. Such an impact will continue until the surface of the anode layer is completely impaired. Therefore, the alkali resistance of the anodization layer of the aluminum or aluminum alloy elements is to be improved to address the said problem.
For example, the Chinese Patent Application, the publication number of which is 101270477A, discloses a sol-gel coating disposed on the element subject to the aluminum anodization treatment, which makes the element resistant to environmental impacts and other loads. However, the sol-gel coating formed on the vehicle element could be only applied to special aluminum or aluminum alloy elements subject to aluminum anodization treatment, and is applied on the decorative strips by sparing, scrolling, impregnation, scraping and/or rolling, and then hardened by heating. Therefore, the metallic feel and appearance of the surface of the vehicle elements are poor, the production process thereof could not be controlled well and the cost is high.